In travel writing, dialogue is used above all to talk about encounters with foreigners (the local people). It is much more than just a conversation. As the dialogue progresses, it defines the characters and their relationships and advances the plot (by giving information, describing events, etc.). You will quickly discover that it is not easy to write good dialogue. Indeed, it is perhaps the most technical aspect of all writing and genres. A very useful exercise would be to record and transcribe a conversation that you have had with a friend, for example on Skype. You will be surprised to learn that a real dialogue can sound quite false on paper and vice versa.